When I first saw Jason’s torture scenes in Arkham Knight I thought it was weird that the Joker kept him in his full Robin armor (including his gauntlets and utility belt even) but I attributed it to either a side effect of Bruce’s vision or the game devs wanting to be explicit about his identity; that is, until I realized how humiliating and demoralizing that must have been for Jason. That armor not only serves as a constant reminder of his mentor who “abandoned” and replaced him, but also a reminder of how Jason “failed” as Robin. Jason set out on his own as Robin to kill the Joker because he was haunted by the memory of seeing children’s bodies torn apart by one of the Joker’s cruel schemes, but instead he ends up captured by the very man he hunted.
Imagine how weak and pathetic Jason must feel knowing that even in full armor he can’t endure all of the torture. After months of suffering at the hands of the Joker, Jason whimpers at the sounds of footsteps and cowers in the shadows when the Joker comes near him. Any of us would react the same (and let’s not forget that Jason’s a 15/16 year old kid) but Jason probably held himself up to a higher standard as Batman’s protégé.
In one of Bruce’s visions the Joker says:
“This Robin seems like a real improvement on that last one, Bats. Remember Jason Todd? What a whiner. Always complaining. We’re both better off without that loser.”
I’m sure the Joker never lets Jason forget what a “terrible” Robin he was, using this as justification for Batman replacing him with someone “more worthy” of the title. And after the Joker has completely broken Jason down, ripped away every stitch of pride and self-worth until Jason views himself less than human, Jason probably feels ashamed to even still be wearing his Robin armor :(